The broad, long-term objectives of this proposal are to better understand the role of alcohol in bicycling injuries and to significantly reduce the morbidity and mortality of alcohol-related bicycling injuries. The specific aims are (l) to examine the magnitude of alcohol use in bicycling fatalities, factors related to alcohol use, previous driving-under- influence (DUI) records, and drinking behavior of the fatally injured bicyclists; (2) to examine the magnitude of alcohol use in injured bicyclists admitted to a Level I trauma center, the associations of alcohol use with type and severity of injury, previous DUI records, and drinking behavior; and (3) to examine the effect of alcohol use on the risk of fatal bicycling injury, the risk of non-fatal bicycling injury, and the risk of being fatal when a bicycling injury occurs, while adjusting for potential confounding variables. Bicycling is the leading cause of recreational injury. Bicycling injury results in about 580,000 emergency room visits, 20,000 hospitalizations, and 900 deaths each year in the United States. The estimated annual economic costs of bicycling injury are over $1 billion. Alcohol use is recognized as the most important personal risk factor in motor vehicle injuries and about 90% of bicyclist fatalities are due to collisions with motor vehicles, but very few studies have examined the role of alcohol in bicycling injuries. Using a multi-faceted case-control design, this project will collect and analyze data on teenage and adult bicyclist fatalities (fatal cases, n=80), bicyclist trauma patients (non-fatal cases, n= 120), and site- and time-matched bicyclists who are not injured (controls, n=400). Data will include medical examiner records, trauma registry records, driving records, interviews, and breath alcohol tests. The potential dose-response effect of alcohol on bicycling injury and interaction effects with age, gender, and helmet use will be determined using multivariate statistical techniques. In addition, alcohol use and related factors in drivers who were involved in fatal collisions with bicyclists will be examined at a national level using the Fatal Accident Reporting System data of the National Highway. Traffic Safety Administration. The results of this project can be used to develop public policies (e.g., regulating alcohol use by the people biking on public roads) and education programs for prevention and control of bicycling injuries.